Unable to reset reports using setReport method

Hello,
When I set the report using `setReport` method. I get this message below

 Uncaught TypeError: Cannot assign to read only property 'uniqueName' of object '#<Object>

I am trying to update a report that looks like

{
   "dataSource":{
      "type":"csv",
      "filename":"https://<path-to-remote-csv>",
      "requestHeaders":{
         "Authorization":"Bearer <Token>"
      }
   },
   "options":{
      "grid":{
         "type":"flat"
      }
   },
}

with one that looks like

{
   "dataSource":{
      "type":"csv",
      "filename":"https://<path-to-another-remote-csv>",
      "requestHeaders":{
         "Authorization":"Bearer <token>"
      }
   },
   "slice":{
      "rows":[
         {
            "uniqueName":"0_Date.Year"
         },
         {
            "uniqueName":"0_Date.Month"
         },
         {
            "uniqueName":"0_Date.Day"
         },
         {
            "uniqueName":"1_Review"
         },
         {
            "uniqueName":"2_City"
         },
         {
            "uniqueName":"3_Type"
         },
         {
            "uniqueName":"statement_expression"
         },
         {
            "uniqueName":"language"
         },
         {
            "uniqueName":"statement_topic"
         },
         {
            "uniqueName":"statement_opinion"
         },
         {
            "uniqueName":"sentiment"
         },
         {
            "uniqueName":"group_topic"
         },
         {
            "uniqueName":"group_opinion"
         }
      ],
      "measures":[
         {
            "uniqueName":"4_Price",
            "aggregation":"sum"
         },
         {
            "uniqueName":"group_uniq_doc_count",
            "aggregation":"sum"
         }
      ],
      "flatOrder":[
         "0_Date.Year",
         "0_Date.Month",
         "0_Date.Day",
         "1_Review",
         "2_City",
         "3_Type",
         "4_Price",
         "statement_expression",
         "language",
         "statement_topic",
         "statement_opinion",
         "group_uniq_doc_count",
         "sentiment",
         "group_topic",
         "group_opinion"
      ]
   },
   "options":{
      "grid":{
         "type":"flat"
      }
   },
   "version":"2.8.12",
   "creationDate":"2020-08-12T16:27:31.704Z"
}

If I remove the slice field from the second report then it works fine. Would very much appreciate any help.
 
Cheers,
Ali